Lu Yun-Bi, Franze Kristian, Seifert Gerald, Steinhäuser Christian, Kirchhoff Frank, Wolburg Hartwig, Guck Jochen, Janmey Paul, Wei Er-Qing, Käs Josef, Reichenbach Andreas
Department of Pharmacology, School of Medicine, Zhejiang University, Yan An Road 353, Hangzhou 310031, China.
Proc Natl Acad Sci U S A. 2006 Nov 21;103(47):17759-64. doi: 10.1073/pnas.0606150103. Epub 2006 Nov 8.
One hundred fifty years ago glial cells were discovered as a second, non-neuronal, cell type in the central nervous system. To ascribe a function to these new, enigmatic cells, it was suggested that they either glue the neurons together (the Greek word "gammalambdaiotaalpha" means "glue") or provide a robust scaffold for them ("support cells"). Although both speculations are still widely accepted, they would actually require quite different mechanical cell properties, and neither one has ever been confirmed experimentally. We investigated the biomechanics of CNS tissue and acutely isolated individual neurons and glial cells from mammalian brain (hippocampus) and retina. Scanning force microscopy, bulk rheology, and optically induced deformation were used to determine their viscoelastic characteristics. We found that (i) in all CNS cells the elastic behavior dominates over the viscous behavior, (ii) in distinct cell compartments, such as soma and cell processes, the mechanical properties differ, most likely because of the unequal local distribution of cell organelles, (iii) in comparison to most other eukaryotic cells, both neurons and glial cells are very soft ("rubber elastic"), and (iv) intriguingly, glial cells are even softer than their neighboring neurons. Our results indicate that glial cells can neither serve as structural support cells (as they are too soft) nor as glue (because restoring forces are dominant) for neurons. Nevertheless, from a structural perspective they might act as soft, compliant embedding for neurons, protecting them in case of mechanical trauma, and also as a soft substrate required for neurite growth and facilitating neuronal plasticity.
150年前，神经胶质细胞作为中枢神经系统中第二种非神经元细胞类型被发现。为了赋予这些新的神秘细胞一种功能，有人提出它们要么将神经元粘在一起（希腊语“γλαῖα”意为“胶水”），要么为神经元提供一个坚固的支架（“支持细胞”）。尽管这两种推测仍然被广泛接受，但它们实际上需要截然不同的细胞机械特性，而且从未有过实验证实。我们研究了中枢神经系统组织以及从哺乳动物大脑（海马体）和视网膜中急性分离出的单个神经元和神经胶质细胞的生物力学。使用扫描力显微镜、体流变学和光致变形来确定它们的粘弹性特征。我们发现：（i）在所有中枢神经系统细胞中，弹性行为比粘性行为更占主导；（ii）在不同的细胞区室，如胞体和细胞突起中，机械特性有所不同，很可能是因为细胞器的局部分布不均；（iii）与大多数其他真核细胞相比，神经元和神经胶质细胞都非常柔软（“橡胶弹性”）；（iv）有趣的是，神经胶质细胞比其相邻的神经元还要柔软。我们的结果表明，神经胶质细胞既不能作为神经元的结构支持细胞（因为它们太软），也不能作为神经元的胶水（因为恢复力占主导）。然而，从结构角度来看，它们可能作为神经元柔软、柔顺的嵌入物，在机械创伤时保护神经元，同时也作为神经突生长和促进神经元可塑性所需的柔软基质。
